#include "assembler.h"

namespace l8
{

// -----------------------------------------------------------------------------
// Implementation of Label

int Label::pos() const
{
    if (pos_ < 0)
    {
        return -pos_ - 1;
    }

    if (pos_ > 0)
    {
        return  pos_ - 1;
    }

    UNREACHABLE();
    return 0;
}


// -----------------------------------------------------------------------------
// Implementation of RelocInfoWriter and RelocIterator
//
// Encoding
//
// The most common modes are given single-byte encodings.  Also, it is
// easy to identify the type of reloc info and skip unwanted modes in
// an iteration.
//
// The encoding relies on the fact that there are less than 14
// different relocation modes.
//
// embedded_object:    [6 bits pc delta] 00
//
// code_taget:         [6 bits pc delta] 01
//
// position:           [6 bits pc delta] 10,
//                     [7 bits signed data delta] 0
//
// statement_position: [6 bits pc delta] 10,
//                     [7 bits signed data delta] 1
//
// any nondata mode:   00 [4 bits rmode] 11,  // rmode: 0..13 only
//                     00 [6 bits pc delta]
//
// pc-jump:            00 1111 11,
//                     00 [6 bits pc delta]
//
// pc-jump:            01 1111 11,
// (variable length)   7 - 26 bit pc delta, written in chunks of 7
//                     bits, the lowest 7 bits written first.
//
// data-jump + pos:    00 1110 11,
//                     signed intptr_t, lowest byte written first
//
// data-jump + st.pos: 01 1110 11,
//                     signed intptr_t, lowest byte written first
//
// data-jump + comm.:  10 1110 11,
//                     signed intptr_t, lowest byte written first
//
const int kMaxRelocModes = 14;

const int kTagBits = 2;
const int kTagMask = (1 << kTagBits) - 1;
const int kExtraTagBits = 4;
const int kPositionTypeTagBits = 1;
const int kSmallDataBits = kBitsPerByte - kPositionTypeTagBits;

const int kEmbeddedObjectTag = 0;
const int kCodeTargetTag = 1;
const int kPositionTag = 2;
const int kDefaultTag = 3;

const int kPCJumpTag = (1 << kExtraTagBits) - 1;

const int kSmallPCDeltaBits = kBitsPerByte - kTagBits;
const int kSmallPCDeltaMask = (1 << kSmallPCDeltaBits) - 1;

const int kVariableLengthPCJumpTopTag = 1;
const int kChunkBits = 7;
const int kChunkMask = (1 << kChunkBits) - 1;
const int kLastChunkTagBits = 1;
const int kLastChunkTagMask = 1;
const int kLastChunkTag = 1;


const int kDataJumpTag = kPCJumpTag - 1;

const int kNonstatementPositionTag = 0;
const int kStatementPositionTag = 1;
const int kCommentTag = 2;

// -----------------------------------------------------------------------------
// Implementation of RelocInfoWriter

uint32_t RelocInfoWriter::WriteVariableLengthPCJump(uint32_t pc_delta)
{
    // Return if the pc_delta can fit in kSmallPCDeltaBits bits.
    // Otherwise write a variable length PC jump for the bits that do
    // not fit in the kSmallPCDeltaBits bits.
    if (is_uintn(pc_delta, kSmallPCDeltaBits))
    {
        return pc_delta;
    }

    WriteExtraTag(kPCJumpTag, kVariableLengthPCJumpTopTag);
    uint32_t pc_jump = pc_delta >> kSmallPCDeltaBits;
    ASSERT(pc_jump > 0);

    // Write kChunkBits size chunks of the pc_jump.
    for (; pc_jump > 0; pc_jump = pc_jump >> kChunkBits)
    {
        byte b = pc_jump & kChunkMask;
        *--pos_ = b << kLastChunkTagBits;
    }

    // Tag the last chunk so it can be identified.
    *pos_ = *pos_ | kLastChunkTag;

    // Return the remaining kSmallPCDeltaBits of the pc_delta.
    return pc_delta & kSmallPCDeltaMask;
}


void RelocInfoWriter::WriteTaggedPC(uint32_t pc_delta, int tag)
{
    // Write a byte of tagged pc-delta, possibly preceded by var. length pc-jump.
    pc_delta = WriteVariableLengthPCJump(pc_delta);
    *--pos_ = static_cast<byte>(pc_delta << kTagBits | tag);
}


void RelocInfoWriter::WriteTaggedData(intptr_t data_delta, int tag)
{
    *--pos_ = static_cast<byte>(data_delta << kPositionTypeTagBits | tag);
}


void RelocInfoWriter::WriteExtraTag(int extra_tag, int top_tag)
{
    *--pos_ = static_cast<byte>(top_tag << (kTagBits + kExtraTagBits) |
                                extra_tag << kTagBits |
                                kDefaultTag);
}


void RelocInfoWriter::WriteExtraTaggedPC(uint32_t pc_delta, int extra_tag)
{
    // Write two-byte tagged pc-delta, possibly preceded by var. length pc-jump.
    pc_delta = WriteVariableLengthPCJump(pc_delta);
    WriteExtraTag(extra_tag, 0);
    *--pos_ = static_cast<byte>(pc_delta);
}


void RelocInfoWriter::WriteExtraTaggedData(intptr_t data_delta, int top_tag)
{
    WriteExtraTag(kDataJumpTag, top_tag);

    for (int i = 0; i < kIntptrSize; i++)
    {
        *--pos_ = static_cast<byte>(data_delta);

        // Signed right shift is arithmetic shift.  Tested in test-utils.cc.
        data_delta = data_delta >> kBitsPerByte;
    }
}


void RelocInfoWriter::Write(const RelocInfo* rinfo)
{
#ifdef DEBUG
    byte* begin_pos = pos_;
#endif

#if 0
    Counters::reloc_info_count.Increment();
#endif

    ASSERT(rinfo->pc() - last_pc_ >= 0);
    ASSERT(RelocInfo::NUMBER_OF_MODES < kMaxRelocModes);
    // Use unsigned delta-encoding for pc.
    uint32_t pc_delta = rinfo->pc() - last_pc_;
    RelocInfo::Mode rmode = rinfo->rmode();

    // The two most common modes are given small tags, and usually fit in a byte.
    if (rmode == RelocInfo::EMBEDDED_OBJECT)
    {
        WriteTaggedPC(pc_delta, kEmbeddedObjectTag);
    }
    else if (rmode == RelocInfo::CODE_TARGET)
    {
        WriteTaggedPC(pc_delta, kCodeTargetTag);
    }
    else if (RelocInfo::IsPosition(rmode))
    {
        // Use signed delta-encoding for data.
        intptr_t data_delta = rinfo->data() - last_data_;
        int pos_type_tag = rmode == RelocInfo::POSITION ? kNonstatementPositionTag
                           : kStatementPositionTag;

        // Check if data is small enough to fit in a tagged byte.
        // We cannot use is_intn because data_delta is not an int32_t.
        if (data_delta >= -(1 << (kSmallDataBits-1)) &&
            data_delta < 1 << (kSmallDataBits-1))
        {
            WriteTaggedPC(pc_delta, kPositionTag);
            WriteTaggedData(data_delta, pos_type_tag);
            last_data_ = rinfo->data();
        }
        else
        {
            // Otherwise, use costly encoding.
            WriteExtraTaggedPC(pc_delta, kPCJumpTag);
            WriteExtraTaggedData(data_delta, pos_type_tag);
            last_data_ = rinfo->data();
        }
    }
    else if (RelocInfo::IsComment(rmode))
    {
        // Comments are normally not generated, so we use the costly encoding.
        WriteExtraTaggedPC(pc_delta, kPCJumpTag);
        WriteExtraTaggedData(rinfo->data() - last_data_, kCommentTag);
        last_data_ = rinfo->data();
    }
    else
    {
        // For all other modes we simply use the mode as the extra tag.
        // None of these modes need a data component.
        ASSERT(rmode < kPCJumpTag && rmode < kDataJumpTag);
        WriteExtraTaggedPC(pc_delta, rmode);
    }

    last_pc_ = rinfo->pc();

#ifdef DEBUG
    ASSERT(begin_pos - pos_ <= kMaxSize);
#endif
}


// -----------------------------------------------------------------------------
// Implementation of RelocIterator

RelocIterator::RelocIterator(const CodeDesc& desc, int mode_mask)
{
    rinfo_.pc_ = desc.buffer;
    rinfo_.data_ = 0;

    // relocation info is read backwards
    pos_ = desc.buffer + desc.buffer_size;
    end_ = pos_ - desc.reloc_size;
    done_ = false;
    mode_mask_ = mode_mask;

    if (mode_mask_ == 0)
    {
        pos_ = end_;
    }

    next();
}

inline int RelocIterator::AdvanceGetTag()
{
    return *--pos_ & kTagMask;
}


inline int RelocIterator::GetExtraTag()
{
    return (*pos_ >> kTagBits) & ((1 << kExtraTagBits) - 1);
}


inline int RelocIterator::GetTopTag()
{
    return *pos_ >> (kTagBits + kExtraTagBits);
}


inline void RelocIterator::ReadTaggedPC()
{
    rinfo_.pc_ += *pos_ >> kTagBits;
}


inline void RelocIterator::AdvanceReadPC()
{
    rinfo_.pc_ += *--pos_;
}


void RelocIterator::AdvanceReadData()
{
    intptr_t x = 0;
    for (int i = 0; i < kIntptrSize; i++)
    {
        x |= static_cast<intptr_t>(*--pos_) << i * kBitsPerByte;
    }
    rinfo_.data_ += x;
}


void RelocIterator::AdvanceReadVariableLengthPCJump()
{
    // Read the 32-kSmallPCDeltaBits most significant bits of the
    // pc jump in kChunkBits bit chunks and shift them into place.
    // Stop when the last chunk is encountered.
    uint32_t pc_jump = 0;
    for (int i = 0; i < kIntSize; i++)
    {
        byte pc_jump_part = *--pos_;
        pc_jump |= (pc_jump_part >> kLastChunkTagBits) << i * kChunkBits;

        if ((pc_jump_part & kLastChunkTagMask) == 1)
        {
            break;
        }
    }

    // The least significant kSmallPCDeltaBits bits will be added
    // later.
    rinfo_.pc_ += pc_jump << kSmallPCDeltaBits;
}


inline int RelocIterator::GetPositionTypeTag()
{
    return *pos_ & ((1 << kPositionTypeTagBits) - 1);
}


inline void RelocIterator::ReadTaggedData()
{
    int8_t signed_b = *pos_;

    // Signed right shift is arithmetic shift.  Tested in test-utils.cc.
    rinfo_.data_ += signed_b >> kPositionTypeTagBits;
}


inline RelocInfo::Mode RelocIterator::DebugInfoModeFromTag(int tag)
{
    if (tag == kStatementPositionTag)
    {
        return RelocInfo::STATEMENT_POSITION;
    }
    else if (tag == kNonstatementPositionTag)
    {
        return RelocInfo::POSITION;
    }
    else
    {
        ASSERT(tag == kCommentTag);
        return RelocInfo::COMMENT;
    }
}


void RelocIterator::next()
{
    ASSERT(!done());
    // Basically, do the opposite of RelocInfoWriter::Write.
    // Reading of data is as far as possible avoided for unwanted modes,
    // but we must always update the pc.
    //
    // We exit this loop by returning when we find a mode we want.
    while (pos_ > end_)
    {
        int tag = AdvanceGetTag();
        if (tag == kEmbeddedObjectTag) {
            ReadTaggedPC();
            if (SetMode(RelocInfo::EMBEDDED_OBJECT)) return;
        } else if (tag == kCodeTargetTag) {
            ReadTaggedPC();
            if (*(reinterpret_cast<int*>(rinfo_.pc())) == 0x61) {
                tag = 0;
            }
            if (SetMode(RelocInfo::CODE_TARGET)) return;
        } else if (tag == kPositionTag) {
            ReadTaggedPC();
            Advance();
            // Check if we want source positions.
            if (mode_mask_ & RelocInfo::kPositionMask) {
                // Check if we want this type of source position.
                if (SetMode(DebugInfoModeFromTag(GetPositionTypeTag()))) {
                    // Finally read the data before returning.
                    ReadTaggedData();
                    return;
                }
            }
        } else {
            ASSERT(tag == kDefaultTag);
            int extra_tag = GetExtraTag();
            if (extra_tag == kPCJumpTag) {
                int top_tag = GetTopTag();
                if (top_tag == kVariableLengthPCJumpTopTag) {
                    AdvanceReadVariableLengthPCJump();
                } else {
                    AdvanceReadPC();
                }
            } else if (extra_tag == kDataJumpTag) {
                // Check if we want debug modes (the only ones with data).
                if (mode_mask_ & RelocInfo::kDebugMask) {
                    int top_tag = GetTopTag();
                    AdvanceReadData();
                    if (SetMode(DebugInfoModeFromTag(top_tag))) return;
                } else {
                    // Otherwise, just skip over the data.
                    Advance(kIntptrSize);
                }
            } else {
                AdvanceReadPC();
                if (SetMode(static_cast<RelocInfo::Mode>(extra_tag))) return;
            }
        }
    }
    done_ = true;
}


// -----------------------------------------------------------------------------
// Implementation of RelocInfo

#ifdef ENABLE_DISASSEMBLER
const char* RelocInfo::RelocModeName(RelocInfo::Mode rmode)
{
    switch (rmode)
    {
    case RelocInfo::NONE:
        return "no reloc";
    case RelocInfo::EMBEDDED_OBJECT:
        return "embedded object";
    case RelocInfo::EMBEDDED_STRING:
        return "embedded string";
    case RelocInfo::CONSTRUCT_CALL:
        return "code target (js construct call)";
    case RelocInfo::CODE_TARGET_CONTEXT:
        return "code target (context)";
    case RelocInfo::CODE_TARGET:
        return "code target";
    case RelocInfo::RUNTIME_ENTRY:
        return "runtime entry";
    case RelocInfo::JS_RETURN:
        return "js return";
    case RelocInfo::COMMENT:
        return "comment";
    case RelocInfo::POSITION:
        return "position";
    case RelocInfo::STATEMENT_POSITION:
        return "statement position";
    case RelocInfo::EXTERNAL_REFERENCE:
        return "external reference";
    case RelocInfo::INTERNAL_REFERENCE:
        return "internal reference";
    case RelocInfo::NUMBER_OF_MODES:
        UNREACHABLE();
        return "number_of_modes";
    }
    return "unknown relocation type";
}

#if 0
void RelocInfo::Print()
{
    PrintF("%p  %s", pc_, RelocModeName(rmode_));
    if (IsComment(rmode_))
    {
        PrintF("  (%s)", data_);
    } else if (rmode_ == EMBEDDED_OBJECT) {
        PrintF("  (");
        target_object()->ShortPrint();
        PrintF(")");
    } else if (rmode_ == EXTERNAL_REFERENCE) {
        ExternalReferenceEncoder ref_encoder;
        PrintF(" (%s)  (%p)",
               ref_encoder.NameOfAddress(*target_reference_address()),
               *target_reference_address());
    } else if (IsCodeTarget(rmode_)) {
        Code* code = Code::GetCodeFromTargetAddress(target_address());
        PrintF(" (%s)  (%p)", Code::Kind2String(code->kind()), target_address());
    } else if (IsPosition(rmode_)) {
        PrintF("  (%d)", data());
    }

    PrintF("\n");
}
#endif

#endif  // ENABLE_DISASSEMBLER

} // namespace l8
